Display shows dF or DEFROST; unit stops heating and may run fan only.

Safety first: Turn off power before cleaning coils or accessing sensors.

• Check outdoor conditions: In cool, humid weather, defrost cycles are normal. The unit will resume heating once the coil temperature rises.
• Inspect evaporator coil: Remove the top or side panel and look for heavy frost or ice buildup. If present, allow the unit to thaw completely with power off.
• Clean coil and clear obstructions: Rinse the coil gently with low‑pressure water to remove dirt and debris. Ensure adequate clearance around the unit for airflow.
• Check defrost sensor: Locate the defrost/coil sensor clipped to the evaporator. Ensure it is firmly attached and wiring is intact. Replace if readings are erratic or if the unit stays in dF for an excessive time.
• Control board: If the unit enters defrost frequently in mild weather, the control board defrost algorithm may be malfunctioning and should be evaluated by a technician.